Im looking at trading my car for a 1999 Ram 1500 with 79000 miles. The problem is the owner states that it chugs and has low rpm hesitation and throws a cly5 misfire code. The wierd thing is that he says he had the compression tested and it was fine and that if he runs premium the CEL doesnt come and it runs fine... Any ideas what would be causing it? I dont want to buy the truck and end up with a pile of crap, so im kind of worried about it.

 

Take it to your local mechanic for a brief inspection.

Could be as simple as a spark plug routing problem (there is a TSB in the FAQ section i believe about plug wire routing to prevent crossfires). Or, it could just need a full tune up including plugs, wires, cap, and rotor.

But it could be as severe as a cracked cylinder head. He may have gotten a compression check done, but still isn't worth the risk.

When I bought my Ram (@86k miles) it ran okay, but about a month later it starting missing on cyl 5. I did a full tune up, and it didn't help. Turns out it was a cracked valve seat. The cracked valve seat over the period of about a month burned the valve causing a permanent misfire.

If the compression was have been checked when I bought it, it would have probably read in the acceptable range. After about a month of my ownership, cyl 5 read ~30 psi.

I didn't do the repair myself, thankfully I bought an extended warranty when I got the truck. Dealer parts alone were $870 to replace the driver's side head, not including labor.

In other words, get your mechanic to check it out. Even if he charges a small fee to do so, it'll be worth it.

 

Blown plenum.......

 

could be a couple things. a blown plenum as said by zman would be the first thing to check out. take a dentist mirror and a flashlight and look down the TB to see if there is any oil pooling in the inake manifold. i just replaced mine about a week ago and it made a world of difference. you might also want to check your cat. to see if its plugged. in my case both were bad.